Aircraft navigation requires avoiding land obstacles that have known geographic locations and elevations. One way to ensure that an aircraft does not collide with a land obstacle is to entrust the navigator or pilot to check for obstacles within a flight path. This requires knowledge of the elevation of the aircraft and the terrain in the vicinity of the flight path. It has distinct disadvantages in that it requires vigilance on the part of the navigator and is prone to human error.
Automatic systems have been developed which contain terrain map information for the entire globe or region. These existing systems use radar in conjunction with terrain map information to detect when surface features come within the immediate path of the aircraft. This requires a large amount of storage for the map data and the use of radar limits the predictive ability of the systems. The warning times of these systems are on the order of one minute before collision with a land feature. The present invention reduces storage requirements by only storing the map data corresponding to regions around the flight path of the aircraft or alternatively dynamic loading of map data from a remote storage ground station. It improves safety by comparing terrain features within the flight path each time the aircraft significantly changes speed or altitude. This allows a warning to be updated continuously during the flight of the aircraft. A preferred embodiment of the invention includes interaction with a ground system. The ground system can share the storage of map data for all aircraft serviced by the system and can correlate the exact location of the aircraft with the locations of terrain features. It can then warn the aircraft and/or other navigational facilities of an impending collision with a land obstacle or that a land obstacle is within an alert range. Several levels of warning can be produced with this system.
Technology is already available or is being developed that will allow the practice of the present invention. Global Positioning Systems as described in U.S. Pat. No. 5,594,545 (Devereux, et. al.,) provide positional information to aircraft while in transit. Such a system can be optionally used to provide the positional input to the present invention.
Cellular telephone data communications such as that described in U.S. Pat. No. 4,825,457 can optionally be used to provide the link from the aircraft to a ground station of several embodiments of the present invention. The unique inventive concept of the present invention is the combination of these technologies to achieve an enhanced level of aircraft safety.
In the future, Motorola's IRIDIUM global communications system and Lockheed Martin's Astrolink global communications satellite systems will provide positional information and communications channels which can be used by aircraft enroute. When these technologies are fully available, they can be used in conjunction with the present invention to efficiently produce an improved level of aircraft safety at a low incremental cost.